Patent GB-597693-A (GB)
Title: Improvements in and relating to machines or mechanism for generating shapes or profiles for diamonds and the like
IPC: B24B9/16
Filed: 1945-02-28
Abstract: 597,693. Cutting, lapping or polishing diamonds and the like. JEARUM, F. C. Feb. 28, 1945, No. 5046. [Class 60] In a cutting, lapping or polishing machine for generating shapes or profiles on diamonds or other stones or minerals or hard metals for industrial tool work, or for the jewellery trade, of the type in which the stone is held in a dop carried on a pivoted radial arm which is capable of oscillation to give the dop an arcuate path of movement in a plane normal (or at a suitable angle) to the lapping plane of a rotary cutting disc or lap against which the stone is treated for generating the convex arcuate or faceted shape or profile required and having means for displacing the axis of oscillation of the radial arm relative to the lapping plane consequent upon oscillation of the radial arm, the means comprises a former capable of oscillation with the radial arm and producing displacements parallel to the lapping plane in a co-operating transmission member, which are converted into displacements normal to said plane and applied to the pivot of the radial arm in reduced ratio appropriate for modifying the arcuate path of the dop according to the predetermined dimensions and shape or profile to be generated. A dop (not shown) is mounted adjustably on a radial arm 2, the pivot spindle 3 of which is mounted in a table 5 supported by a parallel link suspension comprising side frames mounted on lower shafts 7 carried by suspension links 8 from upper shafts 9 mounted in bearings in the machine frame. A bed 10 carried by the side frames has mounted thereon a plate 12 movable in a path parallel with the lapping plane 100, this movement being effected by the engagement of a bar 18, mounted on the plate 12, by rollers 17 carried by a triangular former plate 16 secured to the pivot spindle 3, so that rocking of the radial arm 2 causes reciprocation of the plate 12. This is converted into movement of the pivot spindle 3 towards and away from the lapping plane 100 by means of a roller 15 carried by the plate 12 and engaging a bar 20 carried by a plate 24, the ends of the bar being held by spring-pressed plungers against pins 29 carried by slider bars 28 mounted in the plate 24. One slider 28 is adjustable by screw 143 to set the bar 20 parallel to the lapping plane ; the other slider 28 is adjustable by screw 43 to give the required slope to the bar 20. The plate 24 is adjustable towards and away from the lapping plane, having a depending pin 33, the end of which engages a longitudinal slot 35 in a slide 36 adjustable by means of a screw 38 having a milled head 41 ; the plate 24 also has an upstanding pin 47 in the path of a slider 48 moving on a slideway 49 secured to the machine frame, the slider being adjustable by means of a feed screw 50. During the operation of the machine, the screw 50 is turned to permit movement of the plate 24 and therefore of the pivot spindle 3 towards the lapping plane, the extent of this movement being determined by the setting of the screw 38. When the radial arm 2 is in its mid position, both rollers 17 engage the bar 18, thus giving a centring effect. A bell-crank lever may be provided to hold the plate 12 and bar 18 thereon out of range of the rollers 17 so that the controlling mechanism is ineffective. The table 5 is urged towards the lapping plane gravitationally by means of a lever counterweight device. Interchangeable former plates, carrying one or more rollers positioned appropriately for the shape to be generated, may be used, and also interchangeable abutment bars which may be of curved, angular or faceted form on each side of the mid point. Specifications 565,399 and 576,856 are referred to.